Infection with the hepatitis C virus (HCV) is the most common cause of chronic hepatitis in the United States. HCV is classified into one of six different genotypes, each composed of a variety of related subtypes. One of the most important predictors of the response of patients to antiviral therapy for HCV infection is viral genotype. Currently, infectious HCV that are able to replicate autonomously in tissue culture are available only for genotypes 1a, 1b and 2a. This application aims to create cell lines that are persistently-infected with new isolates of HCV for drug development applications. Our strategy is based on the use of a licensed technology that increases the replicative ability of HCV in tissue culture. We will try to infect various cell lines with six clinical samples containing various isolates of HCV by using this technology. Partial success will be defined as the isolation of a cell line persistently-infected with a new genotype or subtype of HCV that can be used for antiviral evaluation assays. Complete project success will be indicated by our ability to culture all of the clinical samples of HCV utilized. If the HCV found in clinical samples can be propagated in vitro, then a true phenotypic assay of drug resistance in clinical samples could be developed. Our efforts will ultimately help expedite drug development for HCV, leading to improvements in Public Health. [unreadable] [unreadable] One of the most important predictors of the response of patients to antiviral therapy for hepatitis C virus (HCV) infection is viral genotype. Currently, only three isolates of HCV that can replicate in tissue culture are available. This SBIR application aims to create cell lines that are persistently- infected with new clinical isolates of HCV. If the HCV found in clinical samples can be propagated in vitro, then other viral genotypes could be used during drug development and a true phenotypic assay of drug resistance in clinical samples could be developed. This would help expedite drug development for HCV, leading to improvements in Public Health. [unreadable] [unreadable] [unreadable]